Milo g



M. G. KELLOGG. MULTIPLE SWITGHBGARD.

Patented Oct. 26

1v., $11 fr (No Manel.)

VM K

`vention.

STATES PATENT Fries.

MILO G. KELLOGG, `OF CHICAGO, ILLINOIS, ASSIGNOR TO TIIE KELLOGGSVVITCHBOARD AND SUPPLY COMPANY, OF SAME PLACE;

NIU LTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,310, dated October26, 1897'.

Application led November 29, 1889. Serial No. 332,012. (No model.)

To all whom, t may con/cern.-

Be it known that I, MILO G. KELLOGG, of Chicagodllinois, temporarilyresiding at Stuttgart, in the Empire of Germany, have invented certainnew and useful Improvements in Multiple Switchboards forTelephone-Exchanges, of which the following is afull, clear, concise,and exact description, reference being had to the accompanying drawings,forming a part of this specification.

My invention relates to' a telephone-ex change system in which thesubscribers lines are metallic-circuit lines, 'connected to multipleswitehboards and it consists in a system of testing at any board todetermine whether any line is in use. I place as many switchboards inthe central office as are found necessary o1' desirable in order toproperly answer the calls and connect and disconnect the subscriberslines. On each board I place for each line a spring-jack or other switchhaving two contact-pieces which are insulated from each other except bythe circuit lconnections. Said switches are each adapted to receive aloop-switch plug, and when a plug is inserted to connect the twocontact-pieces of the plug with the two contact-pieces of the switch,respectively, one of the contactpieces of each switch should be soplaced that a test-plug or similar device may be readily applied to itor so connected to a Vtest-bolt that it can be readily connected withit. At each subscribers station is a battery, which for purposes oftesting should be so placed and connected that it sends a current toline when the subscribers telephone is in position for use and should beso switched that it sends no current to line when the telephone is inits position where it is not in use-*that is, on the switch. Thisbattery may be the same as that which is used with thetelephonetransmitter.

Figures l and lb of the drawings are front views of sections of twomultiple switchboards to which the same lines are connected. Fig. 2 is adiagram of the boards and their circuits and connections, illustratingmy in- Fig. 3 shows an operators cord sysrem adapted to be used wi ththe switchboards. Fig. 1i is a diagram of the subscribers-stationapparatus, illustrating my invention.

In the drawings like parts and apparatus are indicated by the sameletters of reference.

In Fig. 2, A is asectional view of the switchboard shown in Fig. 1f, andA is a sectional viewof the switchboard shown in Fig. l, each asindicated by the line d e.

a b represent rubber strips, ofthe shape substantially as shown, onwhichthe metal parts of the switches are mounted. lThese strips may beof a length to receive any convenient number of switch parts.

Z l are square holes through the fronts of and at the edges of thestrips adapted to receive and guide the switch-plugs. Thecontact-springs g g are mounted to the rear of and are parallel to theholes Z Z, to which they belong, as shown. jj are contact-pieces of theswitches so placed'as to make the switch 'connections hereinafterdescribed and also to be readily connected with a test-plug for purposesof testing. The switch-plugs are substantially as shown in Fig. 3. Theseveral parts are so made, shaped, and adjusted that when a switch-plugis insertedI into a switch the two contact-pieces ofthe plug formconnection, respectively, with the two contactpieces of the switch.

w and :n in Fig. 2 are two line-annunciators in the central office forreceiving signals from the subscribers stations.

In the operators cord system shown in Fig. `3 only one pair of cords,with its plugs, switch, clearing-out annunciator, telephone, and callinggenerator or battery, is shown. Other pairs with their parts could beadded and connected in a manner which will be apparent to those skilledin the art. One system of pairs of cords is placed at each board for anoperator, and the parts are so mounted that the operator canconveniently operate the board.

The two plugs D and D' are composed of insulating materialn, upon whichare mounted two plu g-contacts m and m', normally or when the plugs areat rest, cross-connected by the conducting base-plate o. The twocontacts m' are connected together by a iiexible conductor CZ. The twoplug-contacts 'fm are connected together by a flexible conductor d, inthe circuit of which is a looping-in switch Y, adapted to be placed uponpairs of contactbolts q q', r r', or s s and thereby loop into thecircuit the clearing-out annunciator fu, the operators telephone set t,or the alternating call-generator B. When one plug is IOO inserted intoa switch of a line, the circuit of this apparatus is completed throughthe crossconnected contacts of the other plug. This cross connection isassisted by the weight which is usually used with a iieXible cordconductor. One of the contact-bolts r" is grounded, as shown, so thatthe plug connected to the other bolt r may be used for testing wheneverthe looping-in switch Y rests upon these bolts. In this way an operatorstest outt is provided, and in Fig. 3 this test outfit may be traced fromtheco-ntact fm of the plug D, flexible conductor d, one lever of thelooping-in switch Y, contactbolt r', telephone set t, to the othercontactbolt r', which is grounded at G.

vEach operator needs only one calling-generator and one telephone forher cord system.

She should have as many looping-in switches and clearing-outannunciators as she has pairs of cords.-

In the subscribers station apparatus shown in Fig. 4 lis thecalling-generator, 2 is the signal-bell, 3 is the transmitter, 4l is theprimary of the induction-coil, 5 is the secondary of the induction-coil,6 is the transmitterbattery, 7 is the telephone-switch, and 8 is thehand-telephone. These parts may be of the usual forms and are connectedas shown or in other suits.

In the drawings one side or branch of the line-say wire No. lb-isconnected to the metal frame of the generator. The other side or branchof the line is connected to the insu- A lated spring s, which bears onan insulated l connected with the ground through a normally-closed key,and point q is connected to the wire which leads to spring s.

The calling-generator is constructed as follows: It has an automaticdevice (shown in the drawings) by which when the crank is not in motionthe wire of the armature is shunted and the line is disconnected fromthe ground at the subscribers station, and when 'it is turned oroperated the shunt is automatically removed from the armature and theline is reason for this will hereinafter be apparent. The automaticdevice shown in Fig. 4 comprises the usual V-shaped attachment 9,

' loosely mounted on the arbor of the driving- Wheel and rigidlyconnected to the drivingwheel. The pinlO on this arbor normally engagesthe V-shaped attachment in such a way ways to produce the required rethepurpose of testing.

circuiting contact q. `When the wheel is pressed outward, the pin v10slides into the middle of the V-shaped attachment.

The contact-points and the circuits are substantially as shown and suchas will produce i the results which I have described above.

The generator should be connected into the line-circuit, so that thetemporary ground is made between the normally open end of the Isubscribers line and the armature-coil.

In Fig. 4 I have represented the gravity- I switch 7 ordinarily usedwith the hand-telephone 8.

It is of course obvious that any other kind of switch may be used aslong as substantially the same functions are accomplished.

The connection of a subscribers line may be traced from test-contacts 7'in cach of the line-jacks, line conductor No. 1b, to the subscribersstation, the generator l normally short-circuited by the conductor 11,bells 2, short circuit 12, switch-lever 7, contact 13, normallyconnected thereto, short circuit 14, line-Wire No. 1, to central,annunciator Qc to ground at G. When the telephone is removed from thehook,the subscribers circuit is transferred as follows: line conductorNo. 1b, cony tact 15,switch-lever '7 ,connected thereto while thetelephone is switched for use, contact 1G, transmitter and test-battery6, secondary coil 5 of the induction-coil, hand-telephone S, and lineconductor No. 1. At the same time the following local circuit isestablished: switch lever 7, conductor l2, transmitter 3, primary coil4, battery 6, and contact 16, connected to the switch-lever under theconditions described. Battery 6 is thus connected in derivation with thelocal transmitter-circuit and the line-circuit. The amount of currentcirculating in these two circuits depends upon their comparativeresistances. The current circulating in the line-circuit is utilized forVhenevcr the two IOC) IIO

conductors of the line-circuit are cross-con- 2 nected through a test:receiving instrument,

the test receiving instrument will sound or J givev a click in responseto this current. This l click only occurs when the telephone is iswitched for use and is prevented when the telephone is restored to theswitch and the g subscribers test-battery is left on open circuit.

temporarily connected to the ground.V y The Y G in each case in thedrawings represents a ground connection.

The operation of the system is as follows:

When a subscriber desires to call, he turns I thecrank of his generatorandthercby temfporarily connects his line with the ground, and, sendinga calling-current over it, oper- .ates his line-annunciator at thecentral office. g He then removes his telephone from its switch 1 andthe operator at the central ofiice places D (one of the plugs of a pairof plugs) in:

corresponding with the pair ofY plugs used,

on the .contact-bolts connected with her telethe switch of the linewhere the call is indil cated, and, placing the lever of the switch Y,

phone-loops iinds out what line is wanted. She then places thecontactpiece m of the other plug D of the pair on the contact-piece j ofthe switch of the line wanted as a test. A complete circuit is therebyestablished as follows: from the ground, through the operatorstelephone, to contact-piece m of the plug D, thence to the line throughthe contactpiece j of the line-switch and over the line throughtelephone and battery 6 if the telephone is orf of its switch and backto the office ground through the other branch of the line. If when thetest is thus made the subscribers telephone of the line tested is on itsswitch, there will be no current on the test-circuit therebyestablished, and the test receiving instrument will not respond. It,however,the subscribers telephone is off from its switch, (for use,)there will be a current over the test-circuit established and theinstrument will respond. The operator can therefore determine on testingwhether or not any line is in use. If the test indicates that the lineis not in use, the operator will place the plug D in the switch of theline. The two lines are thereby connected together in metallic circuit.By moving the levers of the looping-in switch belonging to the pair ofcords used the operator may loop her callinggenerator into the circuitof the two lines and send a signaling current over the circuit from hercalling-generator. Again, by mov ing the levers of the switch she mayswitch a clearing-out annunciator into the circuit and so leave it whilethe wires are connected for conversation, and, again, by moving them shemay switch her telephone into the circuit to determine by listeningwhether the subscribers are through conversation. It will be observedthat in this system of switching and testing the office ground of a lineis not removed when a line is switched with another line. This docs notinterfere with the working of the telephone system, as it is well knownthat one ground on a metallic telephone-circuit does not interfere withits operation, nor will the ground connection of the loop interfere withconversation when the operators telephone is looped into the circuit ofthe two subscribers.

The batteries of the different lines should be connected in theircircuits in the same direction-that is, so that each has the same poletoward the permanently-grounded end of its line. Two lines whenconnected togetherin metallic circuit will then have their batteries inopposition to each other in the metallic circuit; but when a test ismade of either of two connected lines the two batteries at thesubscribers stations will be in parallel circuit with each other withreference to the test receiving instrument and will act together and notin opposition in the test receiving instrument.

If the switclrplug D is used for testing, as described, the groundconnection of the pair of cords should be placed between the operatorstelephone and the contact-piece m of the other plug. The other plugcould be used by reversing the position of the ground connection totheother side of the telephone.

The call-annunciators and the clearing-out annunciators should be sorelated to the test* battery as not to be operated thereby. The usualannunciator and the usual subscribers battery answer these conditions.

The plugs D and Dl should be so inserted in the jacks that the contactsm of the plugs make connections with the contacts j of the jacks. Thisis not necessary, for it is obvious that the plugs may be reversed. Thisinsertion is preferable, however, because a subscriber may then operatehis callingan nunciator while connected with another subscriber forconversation by omitting to open the key-contacts 17 in the groundconnection of his outiit, so that when a subscriber operates hiscalling-generator not only does a circuit exist over the metallic lineconductor, but a grounded circuit exists through hiscalling-annunciator, shunting the metallic circuit in such a way thatthe clearing-out annunciator is not operated. Thus a subscriber controlsboth the clearing-out annu nciator and his call-annunciator, and if anoperator has connected him to a subscriber who does not respond to hiscall he may again secure the attention of the operator.

To prevent the operation of the subscribers call-annunciator whileclearing out, the subscriber opens the contact 17.

l/Vhen two lines are connected together and both subscribers hang uptheir telephones and carelessly omit to send in any clearingout signal,the lines are said to be tied up. If now an operator at any other boardtests either of the "connected lines, his test receiving instrument willremain silent, because the subscribers test-batteries will be on opencircuit and the line tested will indicate free The testing operator thenconnects the tested line with the calling-line with the result that thecalling-line forms a bridge across the tied-up circuit, an d when theoperator loops her call-generator into this bridge for calling not onlydo the subscribers bells ring, but the clearing-out annunciator isoperated at the board where the two lines are tied up, and the operatorthereat seeing the disconnection-signal disconnects the tied-up lines.Thus when lines are left in this con dition the condition is dissolvedwhen either line is wanted. Both connected lines would test free and beconnected to and their tiedup connection would be dissolved if they wereboth wanted at the same time. It will. also be observed that althoughthe line-annuncia tors are not cut off from their lines when the linesare switched for conversation they are actually switched from themetallic circuit by the conductor d, containing the clearing-outannunciator, which acts as a shunt around the two annunciators, so thatenough of the clearing-out current is shunted from the line- IOO -subscribers station while his telephone is annunciators to prevent theiroperation. The

circuit of a clearing-out current may be traced from one pole sof thesubscribers generator, line-conductor No. la, to central, to contact gof the switch,where the line is connected through the annunciator to thecommon ground connection, thence through the annunciator of the otherconnected lineto the contact g of the jack, where the other line isconnected, these annunciators being short-circuited by the conductor cl,containing the clearing-out annunciator, connected to the twocontactsprings g g of the two lines, thence over the line conductorsNos. 2 and 2b to contacts j of thelatter line, conductor d', contact jof the former line, line conductor No. lb, back tothe other pole of thesubscribers generator.

Although the ground has been shown as forming part of the call and testcircuits, it is obvious that a metallic conductor might be substitutedtherefor. To effect this, a connection to a common wire would besubstituted for each ground connection. By this system of testing andswitching only two contact-pieces are required for each switch and onlytwo leading-in wires, as inother metallic-circuit multiple-switchboardsystems.

In sending clearing-out signals the subscriber manipulates thenormally-closed key in the ground connection of his generator to openthe circuit and then operates the generator. There is then no circuitthrough the line-annunciators and they will not be operated, but theclearing-out annunciator in the circuit of the lines will be operated.

`I do not herein claim the switching system herein describedirrespective of the test-battery and apparatus herein claimed, as suchswitching system forms the subject of claims in another of my pendingapplications.

I claim as my invention and desire to secure by Letters Patentl. In atelephone-exchange system, a metallic-circuit line normally open at oneend at the central office and permanently grounded at its other end atthe central oiiice and normally grounded there only, in combination withthe transmitter-battery in the circuit of the line at the subscribersstation when his telephone is switched for use and then only, and a testreceiving instrument at the central office grounded onone side andconnected on its other side to a test plug or device adapted to bebrought for testing into connection with the normally open end of theline, substantially as set forth.

2. In a Itelephone-exchange system, two or more multiple switchboards atthe central office, and metallic-circuit lines, each line being normallyopen at one end and connected to the boards and at its other endpermanently grounded at the central office and connected to the boards,and normally grounded there only, in combination with thetransmitter-battery in the circuit of the line at the switched for useand then only, and test receiving instruments, one at each board, eachinstrument grounded on one side and connected on its other side to atest plug or device adaptcd to be brought for testing into connectionwith the normally open end of any line, substantially as set forth.

3. In a telephone-exchange system, multiple switchboards, ametallic-circuit line and switches for the line, one switch on each ofthe boards, each switch having a contactpoint connected to the line andpermanently connected to the ground anda second contactpoint connectedto the line on its other side in combination with thetransmitter-battery in the circuit of the line while the subscriberstelephone is switched for use but not otherwise and test receivinginstruments, one at each board, each instrument grounded on one side andconnected on its other side to a test plug or device adapted to bebrought for testing into connection with said second contact-piece atits board, substantially as set forth. l

4. In a telephone-exchange system, multiple switchboards,metallic-circuit lines, and switches, one switch on each board for eachline, each switch having two contact-points one connected to one side ofthe line and permanently connected to the ground, andthe Vsecondcontact-point connected' to the other side o'f the line, in combinationwith the transmitter-battery in the circuit of each line while itssubscribers telephone is switched for use but not otherwise, and testreceiving instruments, one at each board,each grounded on one side andconnected on its other side to a test plug or device adapted to bebrought for testing into connection with any of said secondcontact-pieces at its board, substantially as set forth.

5. In a telephone-exchange system, two metallic-circuit lines switchedtogether in multiple circuit for conversation and grounded at thecentralofiice and there only, in combination with transmitter-batteries,one at each of the subscribers stations and each in the circuit of itsline while its subscribers telephone is switched for use but nototherwise said batteries being connected in said metallic circuit inopposition to each other, that is, with their.like poles connectedtogether, and a test receiving instrument grounded at one side andconnected on its other side to a test plug or device adapted to bebrought for testing into connection with either metallic-circuit linewith the line-battery between said test connection and said groundconnection, substantially as set forth.

6. In a telephone-exchange system, multiple switchboards, twometallic-circuit lines connected to said boards and temporarilyconnected into a metallic circuit at one board for conversation and saidcircuit being grounded at the central office but not elsewhere, incombination with transmitter-batteries, one at each of the subscribersstations and each in the circuit while its subscribers telephone is IOOIIO

switched for use but not otherwise, said batteries being connected insaid metallic circuit in opposition to each other, that is, with theirlike poles connected together, and test receiving instruments, one ateach of the other boards, each instrument grounded on one side andconnected on its other side to a test plug or device adapted for testingto be brought into connection with either line with the linebatterybetween said test connection and said ground connection, substantiallyas set forth.

7. In a telephone-exchange system, a test receiving instrumentV at oneboard, and two metallic-circuit lines temporarily connected at anotherboard into a metallic circuit for conversation and said circuit beingconnected to one side of said test receiving instrument, in combinationwith transmitter-batteries, one at each of the subscribers stations andeach in the circuit of its line while its subscribers telephone isswitched for use but not otherwise, said batteries being connected intosaid metallic circuit in opposition to each other, that is, with theirlike poles connected together, and a test plug or device at saidfirst-named board adapted to be brought for testing into connection witheither line with the battery between said test connection and saidconnection with the test receiving instrument and said instrument beingconnected on its other side to said test-plug, substantially as setforth.

S. In a telephone-exchange system, multiple switchboards, test receivinginstruments, one at each board and two metallic-circuit linestemporarily connected together for conversation and their circuitconnected to one side of each of said test receiving instruments, incombination with transmitter-batteries, one at each of the subscribersstations, each in the circuit of its line while its subscriberstelephone is switched for use but not otherwise and connected into saidmetallic circuit in opposition to each other, that is, with their likepoles connected together, and test-plugs, one foreach test receivinginstrument and connected to it on the other side, the test-plug at anyboard where the lines are not switched being adapted to be brought intoconnection with either line with the line-battery between said testconnection and said connection of the circuit with the test receivinginstruments, substantially as set forth.

Sl. In a telephone-exchange system, multiple switchboards,metallic-circuit lines connected to the same, switches on the severalboards to connect any two of said lines together in metallic circuit forconversation, said lines when thus connected being grounded at thecentral ofce but not elsewhere, in combination withtransmitter-batteries, one at each subscribers station, each in thecircuit of its line while its subscriber-s telephone is switched for usebut not otherwise, and said batteries being then connected in the samedirection with reference to said office ground cre connection, that is,with their like poles connected together, and test receivinginstruments, one at each board, each grounded on one side and connectedon its other side to a test plug or device adapted to be brought fortesting into connection with any line with the battery (when in thecircuit) between said test connection and said ground connection,substantially as set forth.

10. In a telephone-exchange system, multiple switchboards, testreceiving instruments, one at each board, metallic-circuit lines,switches on the several boards to connect any two of said lines togetherin metallic circuit for conversation, said lines when thus connectedbeing connected to one side of each of said instruments, in combinationwith transmitter-batteries, one at each subscribers station, each in.the circuit of its line while its subscribers telephone is switched foruse but not otherwise, said batteries when thus connected being in theircircuits in the same direction with reference to said connection withthe test receiving instruments, that is, with their like poles connectedtogether, and test plugs or devices, one for each instrument andconnected to it on the other side, each plug being adapted to be broughtfor testing into connection with any of said lines with the line-battery(when in the circuit) between said test connection and said connectionof the line with the test receiving instrument, substantially as setforth.

ll. A test-circuit for a metallic-circuit line temporarily connectedwith another such line, from the ground through a test receivinginstrument to a test-plug, thence to the line tested and through thecircuit of the two lines in parallel circuit and transmitter-batteries,one at each subscribers station, in the circuit when his telephone isswitched for use but not otherwise, to the ground at the central office,said batteries being connected in the metallic circuit of said lines inopposition to each other, that is, with their like poles connectedtogether, substantially as set forth.

l2. A test-circuit for a metallic-circuit line temporarily connectedwith another such line, from one side of a test receiving instrument toa test plug or device at a board at which the line is.not switched,thence to the line tested and through the circuit of the two linestested in parallel circuit, thence to the other side of said testreceiving instrument and transmitter-batteries, one at each subscribersstation, in the circuit when his telephone is switched for use but nototherwise, said batteries being connected in the metallic circuit ofsaid lines in opposition to each other, that is, with their like polesconnected together, substantially as set forth.

MIL() G. KELLOGG.

Witnesses:

Finitions D. KELLOGG, MARGARETHA RIEHL.

IOO

IIO

IZO

